Birchler, F.

Blum, J.

Ha, S.-W

Keller, B.A.

Sittig, C.

Spencer, N.D.

Textor, M.

Wieland, M.

Wintermantel, E.

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Surface Characterisation of Titanium Alloy ImplantsWieland M., Sittig C.u, Textor M.°, Birchler F.2), Blum J.2), Ha S.-W.2), Keller B.A.,Wintermantel E.2), Spencer N.D.υSwiss Federal Laboratories for Materials Testing and Research, berlandstr. 129, CH-8600 D bendorf!) Laboratory of Surface Science and Technology, Department of Materials, ΕΤΗ Z rich, Sonneggstr. 5, CH-8092 Z rich2)Chair of Biocompatible Materials Science and Engineering, Department of Materials, ΕΤΗ Z rich, Wagistr. 23,CH-8952 SchlierenINTRODUCTIONThe excellent biocompatibility of titanium and some ofits alloys, used for Orthop die and dental implants, isintimately connected with the properties of the surface incontact with the biological environment [1]. However,there is still a lack of scientific understanding s to howthe chemical composition and topography of the titaniumsurface influences the perforaiance of the implant in abiological environment In this study the chemicalcomposition and the topography of the surface of com-mercial pure (cp) Ti, Ti6A17Nb (in wt.%), Ti6A14V (inwt.%) and for comparison CoCrMo s well s their effecton the viability of the MC3T3E1 osteoblastic celi-linewere investigated.MATERIALS AND METHODSMaterials: All investigations were performed on discs,15mm in diameter and l mm in thickness for cpTi and5mm in thickness for all alloys. cpTi and Ti6A17Nbsamples were mechanically polished (p) to a mirrorfinish. The polished cpTi and TioAlTNb samples weiepretreated by double ultrasonic cleaning in hexane,acetone and ethanol 10 min for each, with intermediaterinsing in the subsequent solvent. Afterwards sampleswere rinsed in ultrapure water (18.2 ΜΩαη) and passi-vated in 30% HNO3 for 1h. Finally, samples weieultrasonically rinsed in ultrapure water, dried with N2,plasma cleaned in an O2 plasma (0.42 mbar, 2 min.),stored in ultrapure water for 2h, dried with N2 and packedin Al-foil. Polished samples were sterilized at 180°C for3h. Ti6A17Nb, Ti6A14V and CoCrMo were either finelysandblasted (fsb) with glass beads or roughly sandblasted(rsb) with alumina and subsequently cleaned ultrasoni-cally in a detergent The sandblasted samples weresterilized by γ-irradiation.Methods: X-ray photoelectron spectroscopy (XPS) dalawere obtained on a Specs Model SAGE 100 using un-monochromatized Mg Ka radiation at 300W (12kV,25mA) with an electron detector pass energy of 50eV forsurvey spectra and 14eV for high-resolution spectra. Thetopography' was investigated with a UBM System foroptical surface rouhgness measurement using a red laser.Line profiles were obtained with a 1.75mm,1400Points/mm line for polished, 5.6mm,500Points/mm for finely sandblasted and 12mm,150Points/mm for roughly sandblasted samples.Cell culture testing: Cell culture tests were carried outwith MC3T3E1 osteoblastic cell- ne cultured in MEMalpha medium (Gibco) containing 5% fetal bovine semm,lOmM -glycerophosphate, 0.25 mM ascorbic acid,0.2% gentamycin and 0.6% fungizone, at 37°C, 5% CO2and 95% relative humidity. For experiments, the cellswere harvested by trypsinization, followed by seeding onpolished and sandblasted specimens s well s on NaOH-etched glass controls. After 48 hours of incubation, cellviability was determined with a thiazolylblue tetrazolium-bromide (MTT) assay [2]. MTT-fonnazan, produced byintracellular succinate dehydrogenase, was extracted withethanolic HEPES/NaCl. The Solutions were transferred toMicroWell plates (Nunc) and the optical density of thesolution was measured at 560 nm using a multiwellreader (Rainbow, SLT, Austria). A second series of testsamples was fixed with 3% glutaraldehyde in PBS andprepared for scanning electron microscopy (SEM).RESULTS AND DISCUSSIONSurface Roughness: UBM measurements (Tablel) indica-ted that there were small differences between poh'shedcpTi and polished Ti6A17Nb surfaces. SandblastedTi6A14V samples were smoother than correspondingTioAlTNb samples and CoCrMo surface roughnessesAlloycpTiTi6A17NbTi6A17NbTi6A17NbTi6A14VTi6A14VCoCrMoCoCrMoSurface0PPfsbrsbfsbrsbfsbrsbΚ,[μιη]2>0.038 ± 0.0050.015 ± 0.0071.32 ±0.184.05 ± 0.681.00 ±0.083.78 ± 0.290.60 ± 0.042.88 ± 0.14Ro^m] 2)0.050 ± 0.0070.030 ± 0.0141.93 ± 0.465.23 ± 0.361.31 ± 0.105.07 ± 0.490.79 ± 0.063.89 ± 0.27Table 1: Roughness of cpTi and its alloys and CoCrMosurfaces. I} p = polished, fsb = finely sandblasted rsb =roughly sandblasted 2) n = 3; mean values ± Standarddeviations446 Biomedizinische Technik · Band 41 · Erg nzungsband 1 · 1996werc smaller than that of T16A14V surfaces.However.there was a statistically significant differcncebetween the different type of surfaces.Surface Composition: XPS analysis of untreated polishedcpTi and Ti6A17Nb surfaces indicated the presence oftypical atmospheric contaminants, especially C and tosome extent O (Table 2), äs well äs low-concentrationcontaminants such äs Si, Pb, Na, Ca and Zn (<1.0 at%)from the mechanical polishing. After pretreatment, XPSdata indicated clean surfaces withreducedC values andTiAINbOCNcpTi1'18.5±1.6——47.0±1.931.112.1—cpTi2)26.7+0.9—55.711.117.411.5tracesTtöAlTNb"19.510.44.110.30.910.152.410.918.311.0—Ti6A17Nb2)22.210.94.510.51.410.156.111.515.911.6tracesTable 2: XPS analysis (at.%) of polished cpTi andTi6Al7Nb samples (n=5 for each surface; means ±Standard deviations). nuntreated, 2)pretreatedonly traces of N from the nitric acid treatment. Thecleaned surfaces showed an atomic concentration ratio of0.6610.08 for C/Ti and 2.0910.04 for O/Ti compared toC/Ti = 1.7110.25 and O/Ti = 2.5510.14 for untreatedcpTi surfaces. These results correlated with ToF-SIMSspectra (data not shown).The oxide-layer thickness, calculated from the XPSintensity ratio Ti(metal)/Ti(oxide), was about 4 - 5nm foruntreated polished cpTi and Ti6A17Nb surfaces [3] and 5 -6nm for the pretreated polished surfaces.On fmely and roughly sandblasted surfaces, Si, Na, Caand AI from the sandblasting processes were found, äswell äs the contaminants C, O and N (Table 3). Nb wasonly detected on the roughly surface of Ti6A17Nb. V inTi6A14V could not be detected (using unmonochromatizedMg Ka radiation).TiAINbVOCSiNaCaNTi6A17Nb"3.310.24.510.3——52.611.013.811.717.411.06.010.42.410.3—Ti6A17Nb2'9.510.818.411.20.610.152.210.616.811.32.510.5——Ti6A14V"3.810.73.810.4——49.711.519.712.115.310.45.910.41.710.2tracesTi6A14V2;8.910.915.312.9——49.412.623.215.92.810.6tracestracesTable 3: XPS analysis (at.%) of sandblasted Ti6Al7Nband T16A14V samples (n=5 for each surface; mean values+ Standard deviations). 1} flnely sandblasted, n roughlysandblastedCell culture testing: On the Ti-alloy samples cellspreading varied with the different surface topographies.The cells on the roughly sandblasted surfaces were evenlyspread and were often seen to form bridges betweendomains of the surface irregularities. On the finelysandblasted surfaces cell spreading appeared more regulärand smoother. Figure l is a representative graph of oneseries out of three. It shows the activity of succinate-dehydrogenase on the different Substrates. On theTi6A17Nb surfaces higher activity was observed withincreasing roughness indicating a possible influence ofsurface topography on cell viability. However, no majorinfluence of topography was observed on the differenttype of CoCrMo and Ti6A14V surfaces.140-120-"5 100-c '2 80-W ww .^ 60-w .40-;20-0-- T1Trl4-1T.TrlT1T-t-I14 5 6samples8 control1: CoCrMo, fsb2: CoCrMo, rsb3: cpTi, polished4: Ti6A14V, fsb5: Ti6A14V, rsb6: Ti6A17Nb, polished7: Ti6A17Nb, fsb8: Ti6AI7Nb, rsbcontrol: glass etched (NaOH)Figure 1: Activity of succinate-dehydrogenase (MTT) onCoCrMo, cpTi and Ti-alloys surfaces (n=4-6).CONCLUSIONSThe preliminary results of the cell culture testing in thisstudy indicate that topographical characteristics of roughlysandblasted Ti6A17Nb surface enhance the viability ofosteoblast-like cells. More detailed studies concemingosteoblast differentiation will be subject of furtherinvestigations.ACKNOWLEDGMENTThe authors would like to thank Mr. P.-H. Vallotton ofStraumann Institute, CH-4437 Waldenburg and Mr. M.Windler of Sulzer Orthopedics, CH-8404 Winterthur forthe materials. This study was fmancially supported byPriority Program of Materials (PPM).REFERENCES[1] B.D. Ratner; Surface Characterisation of Biomaterials,Eisevier Science Publishers B.V., Amsterdam(1988)[2] T. Mosmann; Immunol. Methods 65, 55-63 (1983)[3] B.W. Gallen; Progr. Surf. Sei 50, 269-279 (1995)Biomedizinische Technik · Band 41 · Ergänzungsband 1 · 1996 447

Surface Characterisation of Titanium Alloy Implants

Surface Characterisation of Titanium Alloy Implants

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